text:
Can TCAS cope with situations involving more than two aircraft?
Most of the information I've seen about TCAS talks about only two aircraft being involved.
It's pretty unlikely, although far from impossible that situations involving three or more aircraft may arise.
In such situations is TCAS expected to detect the situation and offer sensible advice still? Or are all bets off and a series of confusing and conflicting advice the most likely outcome?

TCAS can deal with conflicts with multiple aircraft, a so called Multiple Threat Encounter. It will attempt to resolve the conflict but it will be limited in its options.
Examples of a MTE are rare, one case I can point to is this incident involving an aircraft turning into the approach stream between two aircraft instead of following the last in line.
MIT Lincoln lab has reported on MTEs and the TCAS algorithm performance in 2009. They report the majority of MTEs involved three aircraft, but mention one TCAS MTE involving seven aircraft.

Holy carp, the TCAS engineers definitely earned their money that day...

The link to the Lincoln Lab is now broken. The title of the report is "TCAS Multiple Threat Encounter Analysis", and it's still available at https://web.archive.org/web/20100614005807/http://www.ll.mit.edu/mission/aviation/publications/publication-files/atc-reports/Billingsley_2009_ATC-359_WW-18718.pdf.


text:
Why don't airplanes have smoking cabins?
Is there any airplane model that has a small lavatory-like cabin just for smoking? I have never seen any such planes and that made me wonder why this is?
It would not take much more room than a normal lavatory, make it much less likely that someone will smoke in the lavatory regardless of the ban and provide smokers a way to satisfy their need.
I will have to add that I am not a smoker, just a person with weird ideas/questions.

Related Questions:
• Are there any airlines that still allow smoking on-board flights
• Was smoking banned because of passenger safety or occupational safety?

Totally unrelated, but they do this in Amsterdam in the Winter in certain pubs - the only restriction (due to the smoking ban) is that staff aren't allowed in the smoking room.

They used to have such smoking rooms inside airports.

It costs three or six seats - that is too much for any airline.

Related Question: Are there any airlines that still allow smoking on-board flights?

@ChrisW They still do at Amsterdam/Schiphol :)

Smoking used to be permitted anywhere in the cabin, then relegated to the back rows before being banned altogether. Apart from cost/revenue concerns, installation of a smoking room would be a step backward in health, safety, and social trends.

FWIW, I've heard that there have been fewer problems with outflow valves since the smoking ban. I Googled "outflow valve damage from smoking" and it would seem there is at least some evidence to support this.

@Terry is right. Have you ever seen the goop which accumulated in the ventilation system when smoking was still allowed? The condensate from cigarettes caused all sort of trouble (and was extremely disgusting to remove).

Just off the top of my head,

It would take up space that could be used for three or four paying passengers. This would result in increased ticket prices for everybody and the non-smoking majority have no incentive to subsidise a smoking cubicle.
It would require a ventilation system that would prevent smoky air from getting into the rest of the cabin, which would add weight and complexity.
It's a fire risk and a small fire from some idiot disposing of paper in the ashtray could spread; it would be hard to detect such a fire early because you couldn't just put a smoke detector in the smoking cubicle.  (I guess an infra-red detector would work.)
Almost nobody tries to smoke in the lavatory so reducing the occurrence of an event that hardly ever happens isn't worth much.
Rates of smoking are decreasing in most Western countries, so demand for such a cubicle is already falling.
Anti-smoking legislation is often aimed at worker protection: who's going to clean the smoking cubicle and what equipment will they need?
I doubt there's significant pressure, even from smokers, for such a service to be provided.

On the 3rd point, there are smoke detectors that distinguish cigarette smoke.

On the fire risk thing, remember that during the so called "Golden Age" of aviation, EVERYONE smoked on the plane! How many fires happened because of that?

@Jasmine Plenty. The fire on Air Canada flight 797 probably wasn't caused by a cigarette but the NTSB report on it says (page 61) "While an actual in-flight fire is an extremely rare occurence [...] [reports of smoke in the cabin] often turn out to be smoke from an overheating [lavatory] flushing motor or waste ignited by a discarded cigarette". It's suggested that the captain might have landed that plane sooner if smoke in the lavatory wasn't a fairly common occurrence.

It's against FAA regulations.
Wikipedia says so:

According to FAA regulations, smoking lit cigarettes or anything else that produces smoke or flame is prohibited onboard most commercial aircraft.

The Wikipedia article doesn't reference the FAA regulation and I haven't found it using Google (I only found a document relating to smoking in FAA-controlled buildings).
This 2010 Bloomberg article references nearly 700 law cases brought "by the FAA" (which might corroborate the claim in the Wikipedia article):

The Federal Aviation Administration has brought 696 cases, some for civil fines of thousands of dollars, against people caught smoking aboard airliners in the last five years, said Diane Spitaliere, an agency spokeswoman. Lighting a cigarette on a plane has been banned for 20 years.

That's certainly why we won't see it on US flights - though there are likely places in the world where smoking on aircraft is still legal.

@voretaq7 On the other hand, it means that no airline would fit such a cubicle to a long-haul plane that they might want to use on a route into the USA. Of course, there are many long-haul flights that go nowhere near the USA but that still limits the plane's usefulness somewhat. (And I figure it would only be fitted to long-haul flights.)

I was wondering why not a single airline does it. It's still 25% of adults in the UK are smokers; I would have guessed one airline might try for a competitive advantage by allowing it slightly.

@ChrisW - An aircraft would come under the UK's public smoking laws. Many other European countries have the same kinds of laws.

The regulation you're looking for is 14 CFR 252.3, which states, quite simply, Air carriers shall prohibit smoking on all scheduled passenger flights.

@ChrisW According to the Office for National Statistics, now fewer than 16% of adults smoke; even in 2014, it was only 19%

Regulations are not the reason for anything, they are outcomes from reasons. Hence "it is against regulations" is really not an answer, and the real question, why the regulations are as they are, remains.

During 60's to 70's smoking was not prohibited. However, every rule and prohibition depends on safety, prohibition of smoking on aircrafts also commits to safety of flight. Smoking is a big crime on planes, if there are couple of attempts to smoke on a flight that`s considered as terrorist act, at that point whoever tries to smoke are accused as terrorist. Pilots land aircraft to closest airport and police takes suspects from aircraft.
Possibility of fire is main reason for this rule. Seats or floor could catch fire from cigarettes. Even if you smoke lavatory, it is a lot more dangerous because there are lots of paper towels and etc. that catches fire in lavatories.
Even if some special cabins has been built, there are still risk of fire because of inattention or terrorist could try to burn down the aircraft.
You could say that if somebody tries to burn down an airplane they could use lavatory to that. Because of this aircraft lavatories are equipped with smoke detectors.
Essential of aviation rules to ban everything that could not be controlled up in the air.

I'm not sure about other countries, but I do not believe that someone would be charged with terrorism if they attempted to smoke on a flight in the U.S. They might be arrested for failing to comply with crew instructions and posted placards, but not terrorism (unless, of course, there were actual evidence that they intended to use the cigarette to set the cabin on fire.)

smoking was allowed in the 80s too

I was trying to say: If someone keeps trying to smoke on a particular flight, it will be considered as a terrorist act.

Smoking leads to terrorism charges? [citation needed]

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text:
Is a fuel that reacts with another to form hydrogen for fueling aircraft possible?
Hydrogen is the most abundant element in the universe and has great properties when reacting with oxygen for use as a fuel. Yet here on Earth, its production is prohibitively expensive, its storage without wastage is almost impossible because its molecules are so small no know substance or material can store it safely without leaks. Not to mention safety, as it is highly explosive.
Given its energy density, the above mentioned problems and other inherent problems I did not mention with using hydrogen as a fuel for aircraft, is it possible to come up with a compound or two compounds that can be safely stored in two tanks and have an efficient energy to weight ratio, such that when they react by mixture or process, they produce enough hydrogen to power airliners at the same rate or much more efficiently than with regular fuel?

https://en.m.wikipedia.org/wiki/Hydrogen_production Take your pick.

Whatever your ingredient is, you might as well just burn them directly, minus the incombustible ones like water.

What actual aviation-related problem are you trying to solve?

That's essentially how some liquid fueled rockets work. Which is not a great choice of fuel for a passenger plane.

@verandaguy Im hoping one day the carbon footprint is lowered in aviation, that is the one industry encountering the most difficulty in technical challenges

what has your research shown you so far?  When we ask a question (see [ask]) , we should do some initial research first.

@KorvinStarmast
Chemical hydrogen storage materials like hydrazine, borohydrides etc. are considered potential candidates for this purpose (1).
Nanoparticles, nanoalloys & functionalized nanoparticles are extensively trailed as catalysts for efficient on-demand hydrogen generation from those materials. We are, however, yet to reach a stage where the hydrogen generation is rapid enough to be used in applications such as in an aircraft.

Your title question is rather at odds with the rambling prose in your question's body text.  I have a sugestion.  Re write it so that you clearly take the pithy title, explore some factors in the body, and then actually state the question in the body of your question.  And then, if you have an answer, write an answer to your own question.  Beyond that: the title question is an issue that both automotive and airline industry folks, and various scientists and engineers, have been intrigued by for about 40 years.  (See also fusion for electric power). Your question is, as posed, Too Broad.

Well, yes.  You react the hydrogen with carbon to form moderately long-chain hydrocarbons, say 12-15 carbons, which conveniently form a fairly dense liquid at ambient temperatures.  Then you react those hydrocarbons with atmospheric oxygen to run your jet engine, elimininating the need for a second tank.  Of course if you want to burn your fuel at a high rate, you can add a liquid oxygen supply to the system, for instance https://en.wikipedia.org/wiki/S-IC

Methane can be used to produce hydrogen, and also burned to produce superheated steam (1,000°C required) needed by this process. However you will get more range by just burning methane in much simpler engine.

@h22, the goal is hydrogen production as an alternative to carbon, any combustion that results in CO2 is undesirable, if perhaps the hydrogen stored in methane or some other compound is produced with a requisite or higher energy density than current fossil fuel with some other less harmful carbon by-product then that would be a step in the right direction for carbon emissions, but then again an even better compound would have to be produced removing that by product because it has unnecessary weight and has to be carried around..

Chemical reactions to produce hydrogen (or hydrogen-rich gas mixtures -- acids and metal, steam over red hot iron, or coking coal) were commonly used to produce lifting gas from the early days of ballooning until hydrogen was phased out for dirigibles.
Except for coking, these aren't practical to produce hydrogen for fuel (and coal gas has too many other things in it to be readily converted to a carbon-neutral fuel).  The energy required for the process (heating iron red hot and boiling water, heating coal red hot in a retort, or producing strong nitric or sulfuric acid) is MUCH more than the resulting gas will produce when burned in an engine.  Even reforming (converting light hydrocarbons directly to hydrogen with catalysts) is more useful for the low consumption of a fuel cell than for an engine that will want hundreds of kilos of gas per minute.
Direct electrolysis is currently the most energy-efficient method of producing hydrogen in quantity, but it completely fails to overcome the other practical issues with hydrogen as a fuel (low density, storage problems, effects on materials).  The combination of power density requirement and mass limitations for flight mean we'll probably be burning synthetic hydrocarbons that are direct replacements  for gasoline and kerosene (but hopefully carbon-neutral) for decades before we can completely eliminate combustion engines in aircraft -- if it's ever practical to do so.

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text:
What are the limitations to adding wings with engines to a helicopter?
I've probably seen this in science fiction and cartoons but never in real life. Rotor wing aircraft (helicopters) have numerous advantages over their fixed wing counterparts, and vice versa. For example, helicopters can take off and land vertically and do this almost anywhere. But fixed wing aircraft can fly further, faster and are more fuel efficient than helicopters of similar weight.
What are the limitations to adding folding wings to a helicopter, each equipped with a turboprop or turbofan whose shafts connects with the helicopter fan blade for vertical take off?
Once enough speed is gained from the vertical takeoff helicopter phase, the gearbox connects the turboprop or turbofan, they power it enough for it to generate lift at the fixed wings and when the wings are generating lift, the gear box disconnects the helicopter blades and they fold and are housed in the fuselage (like landing gear) to reduce drag. The fixed wing part of the flight takes over for faster speed, more efficient cruise and better range. The same process applies for landing.
I know there are turbofan aircraft that are a cross, their advantages of fixed wing over rotorwing are limited and their wings do not fold.

Related

Sikorsky S-72 Rotor Systems Research Aircraft had both fixed wings and turbofan engines, though not exactly wings with engines.
https://en.wikipedia.org/wiki/Sikorsky_S-72
http://www.helistart.com/pictures/Sikorsky_S-72.jpg

The V-22 Osprey is quite close to what you describe. The connections from the rotors to the fuselage are in fact wings. During takeoff, it's a rotorcraft, and during flight, it's a fixed wing aircraft. Rather than a gearbox, they opted for rotating engines.
The project was plagued by cost overruns,

Its [The V-22's] production costs are considerably greater than for
  helicopters with equivalent capability—specifically, about twice as
  great as for the CH-53E, which has a greater payload and an ability to
  carry heavy equipment the V-22 cannot... an Osprey unit would cost
  around \$60 million to produce, and \$35 million for the helicopter
  equivalent.
— Michael E. O'Hanlon, 2002.

Another aircraft similar to your idea is the F-35B. Rather than foldable rotors, it has a lift fan which connects to the main engine when needed. This aircraft was also plagued by cost overruns.
The harsh reality in engineering is not that things are impossible, but that they are extremely expensive, and by combining multiple functions in a single airframe, you will always have to find a compromise between either function. Both the F-35B and V-22 are very heavy aircraft due to the engineering complexity, and as such can carry less payload than more dedicated concepts. However, this is deemed acceptable because the U.S. Navy likes their aircraft extremely versatile.
There is also the question of demand. For decades, there has been the idea that aircraft need to be as versatile as possible, but whether this will be the case in the future, remains to be seen. Your concept may be capable of faster travelling and higher payloads than the V-22 (which rotors are too small for heavy lifting and too big for fast flying), but the real question is whether the added weight due to the complexity of this concept will offset the theoretical performance gain.
Finally a technical remark. The most difficult part is transitioning from forward flight to hovering. Rotor blades are very flappy, so how you will manage to deploy them during forward flight (when centrifugal forces do not yet straighten them out, and when the lift vector may be in any direction unless you can carefully control their orientation) remains a large engineering challenge, especially if you want to keep the weight of the aircraft low.

A very promising British design from the 1950s used both, a rotor at low speed and a conventional wing at high speed for lift creation. This was the Fairey Rotodyne, a prototype for a flying bus to connect remote locations with a VTOL aircraft. Its rotor was tip-jet-powered and burned a mixture of fuel and compressed air bled from two wing-mounted Napier Eland turboprops. After take-off, power was switched to the propellers and the rotor was unloaded to minimize its drag at high speed. This way, both lift-creating means could be optimized for their speed domain.
You will notice that the wing is unusually  small while the rotor is unusually large. This allowed both to operate at higher efficiency than wings or rotors which are designed to work over the full speed range. However, the combination of the two weighs more than either a rotor or a wing, which reduced the possible payload of the Rotodyne. Neither was meant to fold away because that would had increased weight even more.

Fairey Rotodyne (picture source Ed Coates collection)
In the end, it was wavering British government support rather than any technical issues which limited the Rotodyne to a single prototype.
Today, the most promising solution seems to be a coaxial rotor with a separate source of thrust; either a propeller or jet engines. The coaxial rotor is slowed down at high flight speed in order to keep tip Mach numbers below 0.9 and the lift asymmetry of conventional helicopters is no problem for a coaxial rotor design, allowing much higher flight speeds.
Folding a wing would not help much: When the wing is not needed (which is at low speed), its friction drag is low. Folding the rotor, on the other hand, makes more sense but so far is limited to a helicopter on the ground in order to reduce its storage space on aircraft carriers. Folding in flight has only been studied conceptually.

Illustration 1B from US patent application 2015/0474290 A1 by Bell Helicopter Textron Inc.

I think the bloody noise it made killed it as well. John Farley, chief test pilot of the Hawker Siddeley Harrier later commented: "From two miles away it would stop a conversation. I mean, the noise of those little jets on the tips of the rotor was just indescribable. So what have we got? The noisiest hovering vehicle the world has yet come up with and you're going to stick it in the middle of a city?" That was the main reason British European Airways (BEA) declined to order any.

@MichaelHarvey You are absolutely right, it was indeed the noise which caused the collapse of support for the Rotodyne.

Yes, but I still like it!

@MichaelHarvey Yes, the concept of flying buses connecting villages and small cities is really attractive. Too bad we still haven't reached this level of technology.

the gear box disconnects the helicopter blades and they fold and are housed in the fuselage

Stopping the rotor is the hard part. Rotor blades aren't terribly stiff and rely on centrifugal force to keep them straight in normal flight. Most blades are hinged and free to flap up and own. Just before the rotor stopped, there would be slow moving blades pointing forwards. Unless it was perfectly aligned, the 100mph+ airflow would fold it back over the hub.
In tests where the rotor was merely slowed a little, this is seen as very large fluctuations in blade lift with angle of attack.
Quite a lot of research was done into stopped rotor designs, usually involving low aspect ratio rotors that looked more like wings, but I don't think they ever flew.
One hybrid I quite like involved a wing on only the retreating blade side, and a lifting tail to counter the pitch-up with speed tendency of a flapping blade. I'm not sure why that has never been used.


text:
What would happen if one smeared a generous amount of grease on the gears of the geared turbofan jet engine
What would happen if one smeared a generous amount of grease on all the gears or parts of the gearbox of the  geared turbofan engine such that no tooth is left without grease to the extent that it is 2cm thick layer of grease and then added the required amount of gearbox oil to the gearbox.  Considering the gearbox run very hot because of the friction and speeds,  would that affect its wear and tear or lengthen the next oil change?

Are you asking how to "improve" servicing, or how to sabotage an engine?

Grease is a lubricantI want to know why a thicker lubricant may or may not be desirable for the engine @ZeissIkon

What grease? Vaseline? Duck fat? Who's doing the smearing, a qualified aviation mechanic or a curious visitor?

Petroleum grease, the type used on axles and bearings, it would be used by a qualified chemical engineer  in an experiment.  I'm sure in coming up with the exact optimal lubricant thickness, engineers do rigorous and numerous test, e.g engine oil thickness for a piston engine will differ from that of gearbox and axles @DanieleProcida

Honestly, if you're seriously considering conducting private experiments with the lubrication of aircraft engines, you may as well actually use duck fat. Anything you do that the manufacturer has not advised in its manuals is going to end badly. At least that way you'd earn some notoriety as "that guy who filled the turbofan with duck fat", because I think that notoriety would be the only thing to be gained from this exercise.

"it would be used by a qualified chemical engineer in an experiment." So, basically, you're asking us what the result of this experiment would be? Isn't it usually the point of experiments that you them, rather than just asking "what-if"s?

For safety consideration I believe we should not consider such questions, I suggest to remove it.

I got the answer I wanted, thank you for the comments however though some unpleasant, but the thank you non the less.  I learnt a thing or two about lubrication

Grease is oil mixed with a thickener, usually a soap-type compound (an oil with a hydroxide termination that makes it solidify and also makes it hydrophilic).
Adding grease to the recommended oil would change the viscosity, temperature/viscosity curve, reactivity, oxidation resistance, and so forth.  If anyone noticed the change on a routine (pre-rebuild) maintenance check, they'd be rrequired to downcheck the engine for a rebuild due to the incorrect lubricant.
It's also very likely that the added volume (2 cm layer is a bunch) would result in an overfill, assuming the recommended amount of the recommended oil was added afterward; this would lead to overheating, leaks, or even blow seals due to pressure build-up in the gear case.
The end result is that adding grease -- any kind of grease -- to the recommended lubricant will be very likely to shorten the service life of the parts it contacts, by altering the properties of the overall lubrication.  The manufacturer spent a lot of time and money designing the lubrication specification, and any change is virtually certain to be a downgrade.
If an A&P did this during a rebuild, and was caught (for instance, due to an in-flight engine failure) they'd be likely to lose their license, potentially even go to jail (for the Federal version of "reckless endangerment" and "malicious property damage" if nothing worse).

Interesting tidbit.... In aviation the mixing of lithium soap base (like Aeroshell33) and clay based (like Aeroshell 7) has caused much grief, as they don't like to live together.  Things were made worse by having both types under the same mil spec (MIL-G-82232) and maintenance manuals often just called for grease by the mil spec number.  Most maintenance manuals have had to add extensive admonitions against intermix of clay and lithium.

The general rule has long been to remove all trace of old grease before regreasing during rebuild (for power tools, never mind aircraft engines).  Of course, there's always a Gomer with a grease gun...

Thank you for the answer I learnt a lot about lubrication and lubicants

On aviation components like screwjack ballnuts or non-sealed grease-charged gearboxes, it's possible to recharge the grease on-wing.  You can't get a 100% purge.

@securitydude5 I am familiar with a particular screw jack actuator that at one time had a gearbox filled with a grease-oil slurry, basically grease diluted with oil to the consistency of a milk-shake.  All that happened was the oil separated from the rest of the grease even faster than normal and leaked out through the dynamic seals, and after 10000 hours the gearbox was caked with dried out grease with teeth worn down to nubs.  A later iteration of the actuator just went with synthetic oil and better seals.


text:
Rocket Thrust vs Air breathing jet engine why is a rocket better
What are design dynamics that give the rocket engine higher thrust than an air breathing jet engine of similar size in comparison to a turbo jet engine, turbo fan engine, high by pass turbo fan engine, Scram jet or ram jet.  Is it impossible to improve any of these engines to match the performance of the rocket in terms of thrust

Your question seems too broad. I fail to understand if it concerns speed limitation of air-breathing jet engine, designs comparision for supersonic engines (either rockets or air-breathing jet engine), thrust limitation, or something else. You should refine your question so that it is more specific. Don't hesitate to take a tour in the help center.

It is simply the rate at which fuel can be burned.  For instance, the Saturn V's first stage carried 1.37 million kg of liquid oxygen (along with the kerosene fuel), which it burned in about 165 seconds.  Imagine the size of the jet intake you'd need for a comparable amount of air.


text:
Should "Thrust Reduction" and "Acceleration" heights be the same for the Boeing 737 NG?
Should the Thrust Reduction height be the same, lower or higher than the Acceleration Height?
In other words, what is their "correct" sequence.
I am referring specifically to the B737NG, if it makes a difference.
And I am assuming no Noise Abatement procedures are in place, nor any obstacle clearance requirements.
Just assume one takes off towards the open sea.
I have already read the thread What determines the "acceleration" and "thrust reduction" heights? but it did not answer my above "simpler" question.
I always thought one does not reduce thrust before cleaning up but reading some posts I am in doubt now.

In my flight simulator I use 0ft acceleration height and once I reach 330 knots I gently pull up and only pull back on the throttle upon reaching 5min of TOGA time. In my experience this yields the shortest time to destination :)

On a more serious note: If you reduce thrust first you usually have to reduce the pitch angle slightly to keep speed. If you reach acceleration height you have to pitch forward again. That can be discomfortable for the pax. If you accelerate first and then reduce thrust you'll create quite a bit of noise for the people on the ground. So I think for passenger comfort and noise abatement keeping the acc and thr red heights the same is the best compromise. Depending on the airport and turns up ahead it may not be practical to accelerate at low altitude, then you increase acc height.

In absence of any other constraints, both thrust reduction and acceleration should be initiated at 1000 feet above aerodrome elevation:

Flap Retraction Schedule
During training flights, 1,000 feet AFE is normally used as the acceleration height
to initiate thrust reduction and flap retraction. For noise abatement considerations
during line operations, thrust reduction typically occurs at approximately 1,500
feet AFE and acceleration typically occurs between 1,500 and 3,000 feet AFE, or
as specified by individual airport noise abatement procedures.

(Boeing 737 NG FCTM 3.32 - Takeoff and Initial Climb)
Regarding your thought of

I always thought one does not reduce thrust before cleaning up but reading some posts I am in doubt now.

It is actually quite normal to reduce thrust before accelerating and retracting flaps. During NADP 1 (Noise Abatement Departure Procedure), which is most common around the world, thrust is reduced first (typically between 800 and 1500 feet) and acceleration is initiated later (typically at 3000 feet). For NADP 2 both occur at the same time. I don't know any procedure where thrust reduction occurs after acceleration.

Both heights can be set independently on the TAKEOFF REF page 2:

Thrust Reduction (THR REDUCTION)
Altitude above origin airport elevation at which the autothrottle reduces from
takeoff N1 to climb N1.
The default value is determined by the airline and is stored in the model/engine
database. The default is displayed in small font.
Manual entries allowed on the ground. Entries must be between 800 to 9,999 feet
and are displayed in large font.
Acceleration Height (ACCEL HT)
Displays acceleration hight for flap retraction.
Default value is from the airline.
Entry is optional. Value is a height from 400 to 9999 feet.

(Boeing 737 NG FCOMv2 11.40 - Flight Management, Navigation - FMC Preflight)

Based on the above, when does the target speed switch from V2+20 to 230 kt and finally to 250 kt?

That depends on the selected pitch mode. When taking off with VNAV armed, it will engage at 400 feet AGL and then command 230 kt at acceleration height and 250 kt when the leading edge flaps are retracted. If you take off without an armed pitch mode, it depends on when you manually select a mode (and of course which mode you select).

"and 250 kt when the leading edge flaps are retracted."
Not when speed passes the "UP" marker in the speed tape?

@StamatisVellis See Why does the FMC in B737 limit the climb speed to 230 knots on the VNAV mode until the leading edge devices are fully retracted?

"For noise abatement considerations during line operations, thrust reduction typically occurs at approximately 1,500 feet AFE and acceleration typically occurs between 1,500 and 3,000 feet AFE, or as specified by individual airport noise abatement procedures." In such a case, the commanded speed between 1,500 and 3,000 ft will stay at V2+20?

@StamatisVellis Yes, that is the normal NADP 1 where you maintain V2+20 until 3,000 ft. This will give you a better climb gradient close to the airport and therefore results in less noise for the surrounding areas.

"If you take off without an armed pitch mode, it depends on when you manually select a mode (and of course which mode you select)." Is it possible to arm another "vertical" mode than VNAV before takeoff?


text:
In the B737, does an IAN NPA require that the G/P is 3° or can the G/P angle vary?
For an IAN Approach to be recognized and work in a Boeing 737, does the Approach G/P need to be exactly 3° or can it vary?

I assume you meant 3° (the typical G/P angle), not 3%?

The G/P can deviate from the typical 3 degrees, but not much.
For any non-precision approach (NPA) flown with VNAV or Integrated Approach Navigation (IAN), the navigation database needs to contain a stored glide path (GP) angle or a suitable waypoint (runway or MAP):

VNAV should be used only for approaches that have one of the following features:

a published GP angle on the LEGS page for the final approach segment
an RWxx waypoint coincident with the approach end of the runway
a missed approach waypoint before the approach end of the runway, (e.g.,
MXxx).

[...]
The FMC
obtains the GP angle displayed on the LEGS page from the navigation database. [...] A GP angle
is coded in the navigation database for nearly all straight-in approach procedures.
[...]
This GP angle is normally defined by the regulatory authority responsible for the
approach procedure and provides a continuous descent at a constant flight path
angle for a final approach path that complies with minimum altitudes at
intermediate step-down fixes. The typical GP angle is approximately 3.00°, but
can vary from 2.75° to 3.77°.

(Boeing 737 NG FCTM 5.45 - Approach and Missed Approach, emphasis mine)
As you can see, the GP angle can vary between 2.75 and 3.77 degrees. For IAN, this G/P information is passed on to the AFDS by the FMC. The list of IAN restrictions does not limit the GP angle:

IAN Requirements and Restrictions

airplanes must be equipped with FMC U10.5 or later and IAN FMA
displays
dual or single engine approaches are authorized
waypoints in the navigation database from the FAF onward may not be
modified
raw data monitoring is required during localizer based approaches.
During FMC based non-ILS approaches, raw data monitoring is
recommended when available in accordance with the techniques
described in the Non-ILS approach section in this chapter
QFE operation is not authorized
cold temperature altitude corrections are not permitted
RNP appropriate for the approach must be used
the autopilot is required until suitable visual reference is established when
performing an approach requiring an RNP of 0.15 or lower.

(Boeing 737 NG FCTM 5.60 - Approach and Missed Approach)
The FCTM does however says the following about when an approach can be flown with IAN:

For FMC based approaches, a proper series of legs/waypoints describing the
approach route including an appropriate vertical path or glide path (GP) angle
must appear on the LEGS page. A GP angle displayed on the LEGS page means
the vertical path complies with final approach step-down altitudes (minimum
altitude constraints). A glide path angle suitable for an IAN approach is one that
approximates 3° and crosses the runway threshold at approximately 50 feet.

(Boeing 737 NG FCTM 5.61 - Approach and Missed Approach, emphasis mine)
It does not say if the full range from 2.75 to 3.77 degrees is considered approximately 3.00°, but it certainly does not have to be exactly 3.


text:
In the B737, does Trim Air require that air supply (by the APU, engines or external) is provided in order to operate?
Will switching ON the Trim Air switch in the B737 provide instrument cooling even without bleed air or external air supply?

Please be more careful with the tags. You created a new tag [b737] instead of using the existing [boeing-737] tag. Creating new tags should only be done when you are sure they are needed.

Also, consider that the subject & body of your question are phrased opposite each other. A "yes" answer to one would be a "no" to the other (which is why my answer says what it does, rather than starting with yes or no).

I started typing b737 and the tag appeared. How could I know it did not exist till now? Usually, when I type a tag that does not exist, the system does not let me post it. Apologies.

The Trim Air switch will accomplish nothing without bleed air.
That switch exists when you have more temperature zones than packs -- in a 737-800, two packs & three zones (flight deck, forward cabin, aft cabin).  To make that work, the packs produce conditioned air at a temperature (i.e. the produce enough cold air) to satisfy the coldest temperature demanded, and then hot bleed air is added to the airflow going to the zones that don't need to be quite that cold.  In contrast, in a 737-700 (two packs & essentially two zones), the left pack delivers air to meet the demand of the flight deck temperature controller, and the right pack delivers air to satisfy the temperature control for the cabin.  Simple, and no trim air switch at all -- nothing to trim.
This all works when there is bleed air.  That's what powers the packs, and that's what's added to the pack output to adjust (trim) the temperature.  Without bleed air, there is nothing to trim (no pack output), and there's nothing to trim with.
If there isn't any pack output and no external air, then instrument cooling is provided by the recirc fans, only. (And you hope it isn't a hot, sunny day, because things can get warm pretty quickly in that condition, especially with an airplane full of people!)


text:
What profile will a Boeing 737 NG follow after pushing the ALT INTV button?
If one uses the ALT INTV button during a Climb or Descent in the Boeing 737 NG on the MCP, what profile (Speed/Path) will the AP follow in such a climb and/or descent? Is it the same as programmed in the CLB and DES pages of the FMC?

What happens when pushing the ALT INTV button depends on the currently selected mode. You can find a full description from the FCOM in this answer.

VNAV Climb: The aircraft will remain in VNAV Climb mode and will follow the profile as programmed in the CLB page on the CDU.
Cruise: The aircraft will start an early descent:

Early Descent
To start an early descent, use DES NOW prompt on the DES page. An early descent can also be started by pushing the altitude intervention switch.

(1) DES NOW (VNAV PTH)
With a VNAV path descent planned, VNAV starts an early descent at 1000 fpm
  and captures the idle descent path. VNAV uses FMC SPD for the autothrottle
  mode and VNAV PTH for the pitch mode.
(2) DES NOW (VNAV SPD)
With a VNAV speed descent planned, VNAV starts an idle thrust early descent.
  VNAV does not attempt to capture the VNAV descent path. VNAV uses VNAV
  SPD for the pitch mode and the autothrottle commands IDLE, followed by ARM.

(Boeing 737 NG FCOM 11.31.36 - Flight Management, Navigation - Flight Management System Operation)
So in this case it depends on the VNAV descent that is planned in the FMC. If you have an altitude constraint selected, the aircraft will start a descent at 1000 feet per minute and intercept the idle descent path. Otherwise it will immediately start the speed descent as programmed in the DES page of the CDU.
VNAV Descent: The aircraft will remain in VNAV Descent mode, but the idle descent path can change due to the deletion of an altitude constraint. Should this result in the aircraft no longer being on the idle descent path, the mode will change from VNAV PATH to VNAV SPD and the aircraft follows the speed programmed in the DES page of the CDU. The same thing happens when all altitude constraints are removed.
Any other mode: Nothing happens. The ALT INTV button has no effect on other modes like V/S for example.

If the MCP altitude is above the current cruise altitude, ALT INTV will reset the cruise altitude to what's in the MCP windown & start a cruise climb.  Also, in the latest OFP, what happens with an early descent depends on how far out you are from Top of Descent: it may re-cruise you & initiate a cruise descent to the new cruise altitude at the Mach # generated for Econ speed at that altitude, or it may start an early descent.

@RalphJ Regarding the first part: yes, that is already covered in the other answer. This question was just about the profile flown. Regarding the second part of your comment: it seems my FCOM is too old. It does not mention anything about such a cruise descent, so feel free to add an answer yourself. It seems this is exactly what the OP was interested in...


text:
How to fly an RNAV (RNP) approach with VNAV in a Boeing 737?
Let us assume you are flying a B737NG and you are cleared for an RNAV (RNP) approach which has several legs with different altitude crossing restrictions.

What do you enter in the MCP altitude window? The first, highest crossing restriction, and then keep repeating by entering the next restriction or does one enter the last and lowest one and let VNAV manage the step descents automatically?

If during this gradual VNAV descent procedure you have to use SPD INTV to alter an FMS commanded airspeed, does this "cancel" the VNAV profile, or will it adjust automatically to suit the new manually selected airspeed?

This usually depends on the airline SOPs. The safest thing to do when cleared for the approach is to set the MCP altitude window to the lowest altitude restriction because that way you won't forget to lower it again. As long as the aircraft is descending in VNAV PTH mode, it will follow all altitude crossing restrictions.
When cleared for final approach, one can also set the DA (Decision Altitude) for the approach instead of a crossing restriction into the window. This will allow VNAV to descend further and is required unless IAN  with G/P is used:

The Integrated Approach Navigation (IAN) modes are armed/engaged by
selecting the APP button on the AFDS Mode Control Panel (MCP). Once armed,
the autopilot/flight director will capture and track the localizer/final approach
course and glide slope/glide path.

(Boeing 737 NG FCOMv2 - 4.20.20 - Automatic Flight - System Description)
Once the aircraft is descending on final approach, one can set go-around altitude into the window:

When the FMC is “on approach”, the following features are available:

when preparing for a missed approach and the MCP altitude is set at least
300 feet above the current airplane altitude, VNAV will continue to
command a descent

(Boeing 737 NG FCOMv2 - 11.31.37 - Flight Management, Navigation - Flight Management System Operation)

Using SPD INTV will usually cause the vertical mode to switch from VNAV PTH mode to VNAV SPD mode, which does not care guarantee to comply with crossing restrictions:

If speed intervention is engaged:

during a path descent with flaps up on an idle leg, VNAV switches to VNAV SPD
with flaps down, VNAV remains in VNAV PTH

(Boeing 737 NG FCOMv2 - 11.31.38 - Flight Management, Navigation - Flight Management System Operation)
So if you already have flaps selected, VNAV PTH will remain active. During VNAV SPD operation, it is the pilots duty to ensure all crossing restrictions are met. Once the aircraft goes back on the path, VNAV PTH mode will engage automatically again (assuming you are on a STAR or approach):

A speed descent cannot automatically revert to a path descent, except during
STAR, approach transition, or approach leg with a vertical angle.

(Boeing 737 NG FCOMv2 - 11.31.33 - Flight Management, Navigation - Flight Management System Operation)
Changing the target speed in the FMS will compute a new descent profile. This usually results in the aircraft no longer being on profile and therefore the vertical mode will switch to VNAV SPD as well.
Note that VNAV SPD will not violate altitude restrictions, if possible:

The descent attempts to comply with waypoint altitude restrictions, and will not
violate these restrictions. The VNAV speed descent will not, however, guarantee
the airplane reaches an altitude restriction at the required point.

(Boeing 737 NG FCOMv2 - 11.31.33 - Flight Management, Navigation - Flight Management System Operation)

Problem is that the FMS decreases the target speed way far away from the airport and one has to start using flaps and slow down from way out which is not practical or "traffic flow" efficient.
So, SPD INTV becomes a necessity, to bring speed up again. Which as you have explained switches from VNAV PTH to VNAV SPD and "distorts" the pre-determined descent path, unless flaps are already extended.

But if you already know that the FMS speed at various waypoints is too slow for you, you can just manually insert different speeds with the CDU before you even start the descent. That way you get an optimal descent profile without the need to intervene later. By the way, please use the comment link under answers for comments, not the answer field ;)

So when using LNAV/VNAV for an RNAV approach as above, will VNAV get you down to the MDA (DA) on Autopilot or will it level off the aircraft at the last waypoint (FAF), before the G/P begins?

@StamatisVellis VNAV will let you fly down the G/P until MDA (assuming you have the MDA set in the MCP).


text:
Does a VNAV PTH descent need the Forecast Descent winds?
If VNAV PTH, contrary to VNAV SPD, maintains a given path angle, depending on the CI chosen, and not a given Speed, then in my mind winds shouldn't affect it, since they would only cause the Vertical Speed to be adjusted accordingly in order to stay on that "fixed" path (since winds will alter the Ground Speed)
After all, VNAV PTH has a band of approx. +/- 12 kt (i.e. 24 kt in total) within which it does not "care" what your speed is. All it wants is to maintain the selected Path.
Hence my question: Does one need to fill in the Forecast Descent Winds for a VNAV PTH descent?
Though I can clearly see and understand how they will affect a VNAV SPD descent.
Because if your primary target is maintaining a given Indicated Airspeed, (be it Mach or IAS), then the winds definitely define where you are going to end up on the ground.

Which aircraft? Idle path descent, or geometric path descent?

The B737-800 in particular and its VNAV PTH descent mode specifically. It only has one VNAV PTH descent, I believe it must be what you call "idle path descent" because it is carried out at idle thrust (as long as you stay within a broad band of airspeed)

Yes, a VNAV PTH certainly needs descent winds so as to calculate and construct the most efficient flyable PATH. The PATH as we know. is built backwards from the landing RWY threshold to Top Of Descent (TOD).
Before I continue, I must say that sometimes managing VNAV PTH can become an unnecessarily complex task, if that's where you're coming from. We always have the alternative of lower levels of automation.
Flyability of the PATH means that the airplane should be on the FMC calculated 3 dimensional PATH  as well as the FMC calculated SPD at all times during descent, approach and landing. This depends on accurate depiction in the FMC of altitude and speed limitations, hopefully no changes to the lateral path, ie routing, and accurate wind data etc.
Small components of Head Wind or Tail Wind may not make it impossible to fly the PATH, but as the HW or TW component increases, it can make it very difficult to maintain and the SPD variations, especially in the upward direction and at altitude can be nerve-racking at times on certain types.
Try flying eastbound into TOKYO (Narita) on VNAV with 600+ kts of Ground Speed due 120+kts TW component without feeding the final cruise and descent wind data - guaranteed 'fun'n'games for the pilot and a possible violation. There's an 18,000 ft crossing restriction which, may become impossible to comply with depending on when the pilot catches on to the problem.
There is always recourse to the use of Speedbrakes if the airplane goes above the calculated profile, and Thrust if it goes below that profile. But the use of either of these indicates a deviation from the most efficient descent, and costs fuel.
In the ultimate analysis, @Stamatis Vellis, while one may not bother to put in any winds for  a 40 minute flight at FL 250 with light winds aloft, why willingly transgress the VNAV Speed Band (referred by you as +/- 12 kts), waiting for the FMC to automatically 'flip' from VNAV PTH to VNAV SPD.
VNAV PATH also represents fuel savings - my take is that when a facility exists, why not use it? 2 minutes spent on putting in effective wind forecasts, can make a more optimized, fuel efficient flight, more comfortable speeds, lower workload, more headspace for the pilots to monitor and make better tactical decisions ALL of which has direct safety impact.

It was not a matter of not being bothered to enter them, it was about understanding if and how the info influences a VNAV PTH descent. Now it is understood that the PATH chosen by entering a certain CI is not a fixed angle path for each CI entered but may vary even if the same CI is always chosen, depending on winds. Your explanation was quite clear.

Hahaha  @StamatisVellis

Hahaha  @StamatisVellis, I was talking about myself  "not being bothered to enter them".

You gave me the answer I was looking for, nonetheless :-)


text:
How does ATC handle different kinds of emergencies?
This question deals with the pilot procedures for declaring an emergency.
I wonder how ATC in the US handles different kinds of emergency or quasi-emergency situations, such as:

MAYDAY
PAN PAN
Minimum Fuel
Medivac
etc

Are there multiple levels of priority handling inside ATC, and how do they communicate priority handling from controller to controller?

FAA Order JO 7110.65W - ATC Procedures Read Chapter 10 for emergencies,

Sounds like that's probably the answer, @RonBeyer. If you put it as such, and provide some relevant quotes for at least the 4 situations rbp asked about, I'm sure you'll get some votes.

@FreeMan Looks like it only addresses MAYDAY and PAN PAN, not the others that much.

This list of articles may be of your interest: http://skybrary.aero/index.php/Portal:Emergency_and_Contingency

FAA Order JO 7110.65W - ATC Procedures, Chapter 10 outlines how ATC should handle procedures for emergency situations.
In the very first section though, it says:

10-1-1(d)
  Because of the infinite variety of possible emergency situations, specific procedures cannot be prescribed. However, when you believe an emergency
  exists or is imminent, select and pursue a course of action which appears to be most appropriate under the circumstances and which most nearly conforms to the instructions in this manual.

So, for Mayday and Pan-Pan, it says in 10-1-1(a):

A pilot who encounters a Distress condition should declare an emergency by beginning the initial communication with the word “Mayday,” preferably
  repeated three times. For an Urgency condition, the word “Pan-Pan” should be used in the same manner.

The use of Mayday and Pan-Pan declares an emergency, but doesn't tell ATC about the nature of that emergency. Therefore just saying those words doesn't trigger any particular method for handling the emergency other than probably the controller offloading other traffic and giving you priority handling. It'll probably also trigger a clearing of the airspace around you, and if you are on final or near an airport, a ground hold.
For Medevac:
2-1-4(b) outlines:

Provide priority to civilian air ambulance flights (call sign “MEDEVAC”). Use of the MEDEVAC call sign indicates that operational
  priority is requested. When verbally requested, provide priority to AIR EVAC, HOSP, and scheduled air carrier/air taxi flights. Assist the pilots of
  MEDEVAC, AIR EVAC, and HOSP aircraft to avoid areas of significant weather and turbulent conditions. When requested by a pilot, provide notifications to
  expedite ground handling of patients, vital organs, or urgently needed medical materials.
NOTE−
  It is recognized that heavy traffic flow may affect the controller’s ability to provide priority handling. However, without compromising safety, good judgment must be used in each situation to facilitate the most expeditious
  movement of a MEDEVAC aircraft.

For Minimum Fuel
2-1-8 Outlines:

If an aircraft declares a state of “minimum fuel,” inform any facility to whom control jurisdiction is transferred of the minimum fuel problem and be alert
  for any occurrence which might delay the aircraft en route.
NOTE−
  Use of the term “minimum fuel” indicates recognition by a pilot that his/her fuel supply has reached a state where, upon reaching destination, he/she cannot accept any undue delay. This is not an emergency situation but merely an
  advisory that indicates an emergency situation is possible should any undue delay occur. A minimum fuel advisory does not imply a need for traffic priority. Common sense and good judgment will determine the extent of assistance to be given in minimum fuel situations. If, at any time, the remaining usable fuel supply suggests the need for traffic priority to ensure a safe landing, the pilot should declare an emergency and report fuel remaining in minutes.

(Emphasis mine)
Really you should read through the entire (long) document to see how ATC is supposed to behave for certain situations. Chapter 2, Section 1 has a lot of "emergency" situations, but most of it boils down to giving priority and assistance that the pilot asks for.

In 27 plus years of ATC I don't recall ever hearing anyone use "PAN-PAN". Yup, it's in the book but if it's not an emergency, usually the sound of the pilot or controller's voice is sufficient to recognize an urgent situation.
I knew a supervisor that was in charge of an area once who was alerted to an urgent situation by overhearing the controller asking "...well WHO'S flying the airplane?!?"
I have heard "Mayday" myself, and as a controller there is not a lot you can do to assist except clear a path and coordinate with everyone who can possibly help.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
If AWOS reports IFR conditions but I can see at least three miles, can I take off or land?
The uncontrolled airfield where I have my airplane gets foggy in the morning occasionally, but there have been times when there is just a little fog where the AWOS station sits so it reports 1/4 mile visibility and undetermined ceiling, yet the runway farthest from it is clear and there are no clouds. My flight instructor and ground school instructor said you must always comply with the AWOS reported conditions, yet my flight examiner (I just got my private pilot license) said a pilot can overrule the automated station if it is clearly wrong. Machines can break and are limited to where their position is.
FAR 91.155 talks about visibility, but doesn't mention how it is determined. Flight visibility is determined by the pilot, so I interpret this to mean he can overrule the AWOS if it is clearly wrong.

(d) Except as provided in §91.157 of this part, no person may take off or land an aircraft, or enter the traffic pattern of an airport, under VFR, within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport—
(1) Unless ground visibility at that airport is at least 3 statute miles; or
(2) If ground visibility is not reported at that airport, unless flight visibility during landing or takeoff, or while operating in the traffic pattern is at least 3 statute miles.
(e) For the purpose of this section, an aircraft operating at the base altitude of a Class E airspace area is considered to be within the airspace directly below that area.

Another question about (e), after reading it about 5 times: my airport is class G up to 700 feet, then turns into class E above that. Does (e) mean that if I am at 700 feet AGL, I am still in class G? Of what significance is this?

if you do decide to takeoff, it's very much on your own risk.

Here's a suggestion: take a photo of the runway area just before you take off, so if there is an issue, you can show the photo to prove that the AWOS was wrong.

My suggestion -- buy the airport authority/owner a transmissometer for the far runway for Christmas :) (I'm sure you're not the only pilot who's run into this pickle, based on your description of it)

In the specific case that you mentioned (VFR at an uncontrolled field), you can take off or land because the only legal requirement is to maintain VFR cloud clearance and it's your responsibility at the pilot to do that. The possible downside would be that if you have some kind of accident or incident and the FAA or NTSB investigates, they will take the AWOS reports as the reference for weather conditions at the time. If weather or visibility was relevant to the accident then your decision might be questioned, unless of course there are witnesses who can confirm the actual conditions.
In the case of a controlled field and VFR, ATC will base their actions on the reported conditions so they would tell you that the field is IFR only. One 'workaround' that could be useful is an SVFR clearance, which allows you to operate VFR in an airport surface area even below VFR minimums. You have to request it because ATC can't offer it although they may hint strongly at it to help you out: "the field is IFR, is there anything you'd like to request?" But ATC may not issue an SVFR clearance if the reported visibility is below 1 mile, so in the scenario you mentioned it wouldn't help you. (And note that you need an instrument rating for SVFR at night.)
Under IFR the picture is different. A part 91 IFR flight can legally depart in zero visibility so there would be no issue there, provided that you get your clearance on the ground first, before entering IMC. Legal in this case obviously isn't the same thing as safe, though.
I deliberately didn't answer your second question because I think it would be best for you to submit it as a separate question.

You don't even need an IFR clearance to depart IFR if the airport is in uncontrolled (G) airspace.  You just need a clearance before you enter controlled airspace.

@Ralga, that's true in general but in the specific case where a class G airport is in IMC then you still need an IFR clearance because there's no way to fly there legally under VFR.

No you don't.  A class G airport is in class G airspace, it is not simply an uncontrolled airport in class E airspace as many are.  There are many areas where class G goes up to 14,500 MSL, so you could easily take off IMC, fly somewhere IMC, and land IMC (though I don't know of any published approaches in class G) without ever talking to anyone and be completely legal.

@Ralgha Good point, and I admit I hadn't considered/phrased it properly: I wasn't distinguishing an IFR clearance from an IFR flight. Entering cloud in class G on an IFR flight without an IFR clearance is indeed legal, if you can maintain the minimum IFR obstacle clearance.

OK, so fog being a ground based cloud, then as long as I am clear of the fog/cloud and can see for at least 1 mile in G airspace, I should be legal. Another suggestion would be take a few pictures before departure to prove the visibility was sufficient.

http://www.law.cornell.edu/cfr/text/14/91.155

Actually, if the Class G airport has a tower, you still need to communicate with said tower, even if they don't issue you a clearance.

@Ralgha -- I have only been able to find two IAPs in the USA that have landing courses that live in Golf airspace, and they are the RNAV (GPS) 32 and VOR/DME Z 32 approaches at KTNX.  Unfortunately, 1) KTNX has a tower (Silverbow Tower), so you'd definitely want to be talking to them, 2) the MAPs for both procedures take you into the Echo airspace to the north of KTNX, and 3) unless you're a military "black" guy or a Janet pilot, you'll probably never get to fly the approach -- KTNX is not exactly keen on guests!

" You have to request it because ATC can't offer it although they may hint strongly at it to help you out: "the field is IFR, is there anything you'd like to request?"" -- cute.  Interesting phraseology though-- it's not really true that "the field is IFR" strictly speaking

@UnrecognizedFallingObject - re "- I have only been able to find two IAPs in the USA that have landing courses that live in Golf airspace, and they are the RNAV (GPS) 32 and VOR/DME Z 32 approaches at KTNX. " - maybe I am missing something.  Is KCVO not another example of what you are talking about?  If not, why not?  Thanks.

@quietflyer -- the approach to KCVO is in E airspace down to 700'

According to AIM 5-5-1 paragraph b:

The pilot-in-command of an aircraft is directly responsible for, and is the final authority as to the safe operation of that aircraft.

CFR Section 91.3(a) states:

The pilot-in-command of an aircraft is directly responsible for, and
  is the final authority as to, the operation of that aircraft.

You'll see this pattern throughout the FAR/AIM's. The regulations state what parameters you can operate under, but you're responsible for gathering data from METAR's, TAF's, ASOS and ATIS and other sources and making a decision on weather you are able to comply with VFR weather minima for the class of airspace you're in if you depart.
Regarding your second question: The floor of E is at 700ft so that means if your altitude is 700ft AGL exactly you're still in E but you're subject to the weather minimums of whatever is below it which in your case is class G weather minimums. If the floor of the class E was on top of Bravo airspace, then if you're exactly on the floor you're subject to class B weather minimums. I think it's just anticipating the lawsuit that may arise from someone being exactly at 700ft and claiming they were in class E instead of whatever is below it with regards to weather minimums.

Read 91.157: (d) "The determination of visibility by a pilot in accordance with paragraph (c)(2) of this section is not an official weather report or an official ground visibility report."
Even though this is in 157 not 155, I think that if you were involved in a weather-related incident, the FAA would argue that the OFFICIAL reported weather controls, not the pilots judgment. This is probably what the Instructor means.
However, many uncontrolled fields, such as yours, have non-official automated reporting, which you could argue is advisory and not regulatory. This is probably what the Examiner means.

A couple of points that may not have been adequately covered yet--
Your question mentions FAR 91.155(d).  But in your example, you are not "within the lateral boundaries of the surface areas of... Class E airspace designated for an airport".  The airspace described by that phrase is the airspace within dashed magenta lines, where Class E airspace comes all the way down the surface.  (See for example KSHR-- link to sectional chart.)  So FAR 91.155(d) has no bearing on your situation.  You only need 1 mile of flight visibility for daylight operations (and even for some night-time pattern work) so long as you don't climb up into the Class E airspace beginning at 700' AGL.  And even if you climbed up into the Class E airspace, where you would need 3 miles of flight visibility, that would have nothing to do with FAR 91.155(d), which would still have no bearing on your situation.
Also, since you are not "within the lateral boundaries of the surface areas of... Class E airspace designated for an airport", you cannot get a Special VFR Clearance for operations at and and near your airport, regardless of altitude.


text:
What are some features of a wing, which effects its lift coefficient other than its sectional view?
What geometrical features of a lifting surface apart from which airfoil it has, I mean the ones visible from the top and front view of a wing (for ex: its span, AR, sweep, dihedral etc.) effects its lift coefficient and in what way? Also its stall characteristics.
I'm not looking for how these features change the total lift a wing produces but its effects on the wings lift coefficient, please correct me if I'm wrong and Cl is only for airfoils.
Edit: I ve found this which explains AR and sweep but how dihedral, anhedral or any other wing modification effects Cl still remains as a question.

Try looking for some equations containing those parameters and see what they each do and what they don’t do.

i couldnt find those equations

@TimothyScherer Try this

Anhedral and dihedral have an effect by causing the vector of lift to be at a slight angle, inward (dihedral) or outward (anhedral). This would also have an effect on induced drag, as do winglets. As far as stalling characteristics go, it is complex enough that it may be best to model it on computer.


text:
Wing incidence angle of tandem wing aircraft
I'm trying to design a tandem wing model aircraft with both wings with the same wingspan. The front wing will have 2 and the rear will have 1 deg of incidence angle, also the front wing will have higher aspect ratio. I'm using Clark-Y airfoil for both wings and active yaw stability will be achieved by differential thrust.
I calculated the neutral point with this website as it gave nice flying results for my older designs.
Usually tandem or canard airplanes have their front wing mounted with a higher incidence but because the front wing has the same span as the rear wing, all of the rear wing will be subject to downwash from the front wing, so I'm concerned if the rear wings angle of attack will change considerably to affect its lift.
How will the rear wing incidence affect the neutral point?
Should I keep the rear wing at 1 deg incidence or should I increase it?

Here is a picture of its approximate form

As a rule of thumb, each degree of AoA of the front wing gives a half degree downwash on the rear wing. Which airfoil are you using? How do you control the airplane? Don't you need a vertical stabiliser?

Thanks, added the info

I am less concerned about your wings than your lack of lateral stability. You can achieve lateral control by means of differential thrust, but not  lateral stability. Please add a fin or winglets at the rear wing.
You are right about downwash affecting the rear wing: Due to downwash it will have a lower lift curve slope which in turn will cause your neutral point to move slightly forward. How much it does depends on the wing's aspect ratio.

Should I keep the rear wing at 1 deg incidence or should I increase it?

I think 1 degree less of incidence will give you moderate longitudinal stability. I would not increase the rear wing's incidence but rather keep some margin to decrease it if flight test shows insufficiently low longitudinal stability


text:
Why do electric versions of helicopters need four rotors, or: why are they quad copters?
Why do electric versions of helicopters need four rotors, or: why are they quad copters?
Could it be that their motor do not have enough torque? Then again electric motors have much more torque than their piston counterparts, which early helicopters used.

Why limit it to 4? Why not six? https://www.google.com/search?q=hex%20copter&cad=h  or 8? https://www.google.com/search?ei=EbXpWoTmHfChggfc4pXoDQ&q=oct+copter&oq=oct+copter&gs_l=psy-ab.3..0i13k1l8j0i7i30k1j0i13k1.42723.44718.0.45838.6.6.0.0.0.0.118.690.0j6.6.0....0...1.1.64.psy-ab..0.6.688...0i7i10i30k1j0i67k1.0.Ahp_ibwP8dM

Possible duplicate of Why haven't quadcopters been scaled up yet?

Convenience, adds impressive abilities, failure is an option
Seeing that there plenty of such toys that have the traditional helicopter layout, there is no "must" involved here.

A typical toy helicopter (image source)
But quads and other multi-rotors have a few of great advantages: symmetry, commonality between the engines, no need for complex variable pitch of the rotors. This makes manufacturing cheaper, and the control algoritms much simpler, allowing for much more autonomy and self-control.
It also allows for some pretty impressive moves that a normal helicopter layout may struggle to replicate (although given the right pilot, it sure can give the quads a run for their money).
Also — as opposed to full scale helicopters — it is not a disaster if a drone fails; failure is an option. Hence the problem of keeping all rotors running flawlessly and perfectly synced — which is an absolute must for a full-sized multi-rotor carrying people, but also a major headache to achieve, often to the point of being prohibitive — is not a problem for the drones.

Well, the main advantage of multi-rotor is that you can do without the complex cyclic control and (in sufficiently small sizes) without any variable pitch at all.

@JanHudec Good point. Added.


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Would installing 6 engines on an Airbus A380 and or Boeing 747-800 achieve a shorter take off distance?
Would installing 6 engines on an Airbus A380 and or Boeing 747-800 achieve a shorter take off distance?  Would that result in excessive acceleration and harmful or uncomfortable G-forces? Would the extra thrust and leverage exert excessive force on the wings?  How about braking,would the braking be shorter if all engines were fitted with thrust reversers

You know that only the two inner engines on the A380 are fitted with reversers? The issues you have adding 2 more engines are structure to hold them (weight), burning more fuel, higher drag, etc. Yes, this will reduce take-off distance (why not just use disposable JATO bottles?), but the expense in fuel consumption and reduced range isn't worth it. These aircraft can't take off from smaller fields anyway (too wide), so why worry about distance?

Yeah why not rockets?

I'd like to suggest you ask such questions differently, e.g. for this one you could just ask "does adding engines allow shorter takeoffs" rather than "if the A380 had 6 engines..." Why? Because if you want to ask for a basic principle, you'll get good answers with extensive details, if you ask for hypothetical changes that will never happen, the question will be frowned upon, because it's missing the counterparts: Added weight and drag, redesign of the wing and tanks, etc. As I assume you're not redesigning the A380, the direct basic question would be better.

A last word: Designing a plane, and anything else actually, is not a matter of having the best solution for each requirement, this is not possible (.g. you may not have the most fuel efficient plane if you also want the most silent engine). There is one major requirement: To be economically viable (you sell the plane to airlines). It's a matter of finding the best compromise to fulfill all requirements. Improving a plane is possible, but an improvement means a better compromise, not a better takeoff distance alone.

The A380-800 as it is has a rather short takeoff capability already; as its wing was designed with the (never built) larger siblings-900 and -1000 in mind, it is very big for the current version. This allows takeoff and landing speeds much (!) slower than the 747.

Would installing 6 engines on an Airbus A380 and or Boeing 747-800
  achieve a shorter take off distance?

Yes in theory, more thrust is faster acceleration.
No, because engine/wing interaction is not simple:

For the 747: the flaps will need an additional thrust gate, which will reduce the flaps capability.
For the A380: since it doesn't have a thrust gate, the additional thrust will create extra drag and pitch down moment, making it harder to lift the nose.
Bolting on engines is unrealistic, as it will require a new wing to take into account the extra forces on the wing.
The extra weight of the engines and their associated systems will increase the weight, which in turn will reduce the acceleration due to the increased normal force on the tires.
The extra engines will intake some of the air meant for the wings, so alongside the reduced capability of the flaps, there goes the full potential of the wing.
After a successful higher-speed takeoff, the extra engines will draw more fuel than needed (jet engines run less efficiently at lower-power). Which will result in a diminished range capability.

Would that result in excessive acceleration and harmful or uncomfortable G-forces?

No, you can use the engines at low thrust if needed.

Would the extra thrust and leverage exert excessive force on the wings?

Idem.

How about braking, would the braking be shorter if all engines were
  fitted with thrust reversers.

Yes, in theory, this could be shorter.
No, with the decreased lift, the airplane will land at a faster speed, so no, not necessarily.


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What is the speed record for the Boeing 747 and Airbus A380?
What are the speed records (true air speed) of these Jumbos: The Boeing 747-8 and the Airbus A380 if any?

indicated airspeed, true airspeed, mach number or groundspeed?

I dont think it is too broad. At most with 4 different speed you need just 8 numbers to come up with.

Probably during China Airlines flight 006's high speed dive

Tokyo -> Honolulu at 708 MPH (ground speed). https://goo.gl/6CVtvD

The published Maximum Operating Mach number (MMO) for the B747 is Mach 0.92 but it can sometimes be exceeded accidentally due to aircraft upset. It has been reported that Mach 0.99 was attained during a Boeing test flight in a slight nose down attitude.
The A380 has a slower MMO of Mach 0.89
The actual true airspeed of a Mach number will depend on the temperature and altitude but at 35,000 feet Mach 0.92 would be about 530 Knots. (610 mph)


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Are nose wheel tyres designed differently from the main wheel tyres?
For the heavy large Jumbos like the Airbus A380 and the Boeing 747-800, considering nosewheel tyres are not subjected to the excessive heating caused by braking from the disks and brake pads, and frictional heat on the outer surfaces caused by contact with the tarmark surfaces and braking, are nose wheel tyres designed and manufactured differently from those of the main gear and do they cost more or less.  Considering they are not fitted with brakes, What is their temperature at landing after and are there instruments to measure this? If not why not?

The last bit is duplicated from your question specifically on tire temperature.

FWIW, for the 747-100/200 aircraft, in general the nose wheel tires are the same as the main gear tires. I say in general because not all 747 models necessarily use the same main gear tires depending on some of the weight upgrades, and also, JALs short-range, high density models had heavier gear as I remember. The main gear wheels had temperature monitoring, but never the nose gear. Don't forget, though, that taxiing exerts considerable side loads on the hose tires when turning.

Wheels on the 747-400 are the same all round.
One operator I worked with had a mixed fleet of -400 and -200s. They used the -200 wheels on the -400 nosewheel (mainwheels had to be -400).


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What happens to unstrapped passengers if the airliner were to fly inverted
If for some reason or the other, because of an emergency, or perhaps craving jail time or did not want her job, or perhaps a girls will be girls moment, a pilot and her captain decided to fly a large aircraft like the A380 or boeing 747 inverted and some passengers decided not to strap on their seat belts per instruction in protest of the girls will be girls stunt, what would happen to the unstrapped passengers if the pilots flew this aircraft inverted for a minute or so at its maximum flying altitude?  Would they land on the ceiling, because acrobatic pilots seem not to when they fly inverted.  Will this aircraft land safely?

I'm voting to close this question as off-topic because it is not a "practical, answerable question based on actual problems that you face" (Help centre).

That depends on how the pilot inverted the aircraft. If they pulled a Tex Johnson and executed a smooth barrel roll everyone would remain in their seats as it is a 1G maneuver. Even the flight attendants pouring drinks wouldn't spill.
If the Pilot executed an aileron roll the situation would be quite a bit different...

You don't see aerobatic pilots hit the roof for two reasons:
When aerobatics are planned and intentional, the pilots are strapped in tight by the seat harnesses (usually 4 or 5 point harnesses). During sustained inverted flight, their harness hold them in their seat.
For simple, quick maneuvers, such as a barrel roll, the maneuver can be be done so that the acceleration will always be "down" relative to the airplane (towards the seat), even when the airplane is upside down.   This is the same principle as swinging a bucket of water over your head and the water doesn't immediately fall out.

In the case you created, it is possible for a wide-body / heavy plane to do a barrel roll and be inverted briefly so that passengers don't fall out of their seats.  Test Pilot Tex Johnson famously did a such a 1G roll in a 707 (although without passengers).
If the flight were sustained inverted flight, however, everyone not strapped down would hit the ceiling.

Yes, they would land on the ceiling if not strapped in.  It is basic physics.  Aerobatic pilots strap in before flying inverted.
Provided the aircraft rolls back upright first, it should be able to land safely.

To be fair the question was ill posted. I need to read again to see OP thinks some pilots don't look to strap themselves while doing stunts. That's wrong because recreational pilots are not acrobatic pilots and both are straped

Yes, I agree... not a well thought out question.

There was an Alaskan Air aircraft that lost its jack screw and flew inverted for a short while. I believe, though, that the fuel lines lacked the means to deliver gas from inverted fuel tanks and basically ran out of gas and went nose first into the Pacific Ocean.


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Calculating forces on a hexacopter which create yaw
I'm trying to design a mathematical model of a hexacopter, and while researching the mechanics of the object I could not figure out how to  calculate the total torque on the drone in 'Z' axis that creates yaw forces. I have found some equations that suggest the torque from one motor is equal to:
[angular velocity]^2 * [some constant] (one source called it the drag constant)

Can anyone explain to me the reasoning behind this equation and how should I approach measuring this constant, given that I have a specific motor to work with.

There are various z-Moments acting on the a Drone. Some frome Accelerating the propellers and others from just rotating the propellers. The Moment you are searching is the result of the drag of the Propeller. This force is always acting in the other direction of the spin direction of the propeller. This Moment also used to control yaw (but isnt as effective as tilting the propulsion unit about some degrees to generate a higher moment expending the attainable moment set). You can find a database of these coefficients with formulas here: https://m-selig.ae.illinois.edu/props/propDB.html
(Maybe you can find your propeller here)
You are searching the Coefficient CQ, so:
M_z = rho * n^2 * D^5 * C_Q
where rho is the density, n the speed in rev/s and D the diameter in m.
To make it easier to understand and see the connection to the drag force I will rearrange the variables in the formula:
M_z = rho * (n*D)^2 * D^2 * C_Q * D
So, n*D can be interpreted as the velocity of the propeller. D^2 can be interpreted as the cross sections therefore resulting in
M_z = rho * V^2 * S * C_Q * D
comparing this to the drag Force:
D = rho * V^2 * S * C_D
We now can interpret the the Last D as a lever arm.
(But in reality this formula comes from de-dimensionizing the moment)
You can measure this Moment from the Output power of the Motor(P_motor_out = P_prop = 2 * pi * n * Q) or from the input power if you know the efficiency of the motor. The best way is to use a torque cell. You can also check, how the measurement were executed in the previously mentioned database.


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What are the eyesight requirements for a medical certificate in India?
Does it matter what your eye power is, if your vision can be corrected to 6/6 (20/20) vision?

Related. You might also like to mention what class of medical you're asking about (if you know), because the requirements can be different for different classes.

Generally in India 6/6 and corrected vision is preferable for eye vision in basic criteria in physical examination, I m not sure if vision is not correct closely they will grant the permission.
But might be link will help you:
http://dgca.nic.in/aic/AIC13_2008.pdf


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What are the differences between symmetrical and cambered airfoils?
I have seen images of cambered and symmetrical wings but apart from that what are the major differences between them?
I have also read that symmetric wings don't produce any lift at 0° AOA whereas cambered wings do.
Also, are the 2 statements given below true?

In a cambered airfoil, the aerodynamic center and center of pressure are not at the same place, so the lift created also generates a moment at the aerodynamic center.
In a symmetric airfoil, the aerodynamic center and the center of pressure are at the same place, so you do not have a pitching moment.

symmetric wings don't produce any lift at 0° AOA whereas cambered wings do.

Yes, that's correct.
Usually, the most important difference is that a cambered wing is optimised for a positive angle of attack. It produces less drag for the same amount of lift, and can produce more lift before stalling.
Obviously that assumes that the wing is the right way up - a cambered wing will be less efficient and stall earlier when inverted. And a symmetrical airfoil will produce less drag when no lift is required (e.g. a vertical stabiliser in steady flight)

Thanks, just wanted to get that confirmed.

A cambered, or "airfoil-shaped" wing cross section will have a significant curve (bulge) on the top surface, usually with the thickest part nearer the leading edge, while the bottom surface will have no or minimum curve. The result of this is that air passing over the top surface of the airfoil has a longer distance to travel than air passing over the bottom surface. This means air on the top surface flows at a higher relative speed. Since Total air pressure = Static (directly onto the airfoil) Pressure plus Dynamic Pressure (speed of the air), and the Dynamic pressure (speed) on the top is higher, that means to balance the total pressure, the static pressure on the top must be lower. The result of all this head-spinning aerodynamics is that the pressure directly on the bottom (at right angles to) surface of the airfoil is higher than that on the top surface, resulting in aerodynamic lift on that wing (airfoil), even at zero degrees angle of attack. If you inverted the airfoil, so the curved surface was on the bottom, there would be negative lift (downward pressure) at zero degrees angle of attack.
On the other hand, symmetrical wings (airfoils) have no aerodynamic camber, but rather have equal distances for the air to travel over both the top and bottom surfaces. This means they will produce exactly zero lift at zero AOA, and require some angle to produce lift.
Finally, to respond to the true-or-false questions about your two statements, it would depend on each airfoil's curvature. The aerodynamic center of any airfoil will be immediately aft of the point of maximum thickness; on a cambered wing, this will be on the top side, usually well forward of the center point. On a symmetric wing, this will probably be near the center point, and equal on both the top and the bottom.
Many of us have demonstrated this when we were children, by putting our arms out the window of a moving car, and pivoting (pronating and supinating) our hands in the wind to produce up and down lift.


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Why does the A320 have an anti skid system and how does it work?
Can somebody explain why do A320 aircraft have an anti skid system? What is its purpose? And a brief explanation on how it works.

Yes, specifically the 320

It's very similar to Anti-Lock-Brakes on cars.

The main reason aircraft have it is that a locked tyre will heat up, wear excessively and can burst (aircraft tyres are typically run at much higher pressure than cars or even HGVs).
If you lock a wheel under braking, it no longer provides any steering. Aircraft might not be swerving around obstacles, but staying on the runway is more important than minimising stopping distance.
A locked wheel generates slightly less than maximum stopping force. An automated system can hold the brakes at the point where it's not quite skidding, and brake harder than a human trying not to skid.

They work by monitoring the speed of each wheel, and releasing the brake on any wheel that slows down significantly more than the rest.
I believe that airliners are tested to check that locked wheel won't wear to the point where it bursts, but you can only do that once!

If AS is inop when landing and you try to brake hard you will almost certainly lock the wheels and blow tires.

Robin, not only the A320 but all modern jetliners have anti-skid.
Like the name suggests the system is to avoid the tires to skid.
It works basically like an ABS but it's actually the ABS 2.0.
The system brakes until just before the tires lock but without modulation like the ABS and it applies more pressure the less is the ground speed. Together with speedbrakes and reverse thrust it applies sufficient brake pressure to keep a steady de-acceleration.
Ex: Autobrake 2 with speedbrake up and NO reverse thrust will have the same stop distance than Autobrake 2 with speedbrake up and Maximum reverse thrust. In this case, the brake pressure applied by the anti-skid will be less with the reverse thrust applied to keep the same stop distance.

Autobrake and anti-skid are separate functions. Anti-skid is active even if braking manually, and just reduces the brake pressure when the wheels start to lock. It is a bit smarter in detecting that than the car systems, but there is no way to find the immediate coefficient of friction, so it still has to be reactionary. The autobrakes is a separete function that manipulates the brakes to achieve target deceleration.

Hi Jan, yes they are separate functions. I did not say otherwise. Thanks for clarifying.


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Do the compressors and turbine rotate at the same speed?
Since the turbine and the compressors are connected to each other via a common shaft, do they both rotate at the same speed. Because I've read that in some jet engines (single spool engines) they don't rotate at the same speed:

Single spool jet engine. These are those jet engines who have one shaft inside them. The compressors and turbines rotate on a same shaft. The speed of compressors and turbines decreases half way down the compressor stages, that is why they can’t match the local airflow. The various turbines and compressors is forced to rotate at same speed which lead to their inefficiencies.

(quora.com)
Is this true?

https://www.quora.com/What-is-the-difference-between-single-spool-and-two-spool-jet-engine. Refer the 1st answer in this link.

Thanks, I added the quote I think you are referring to. If you meant something else, please edit again.

I think your quote is talking about airflow speed rather than the spool speed. That's why more efficient engines have two or three spools, or GTF.

Thx for the edit Bianfable! Yes, that was exactly what I was referring to.

That's one badly-worded quote:

Single spool jet engine. These are those jet engines who have one shaft inside them. The compressors and turbines rotate on a same shaft.

Correct. In a single-spool engine, all of the compressor and turbine stages rotate at the same speed because they're attached rigidly to the shaft.

The speed of compressors and turbines decreases half way down the compressor stages, that is why they can’t match the local airflow.

No, the speed of the compressors and turbines doesn't change. It's the airflow that changes, and causes a mismatch.

English SE could be of assistance

Your question answers itself. If they have a single shaft and no gear box, then they rotate at the same speed. If there is a gearbox then that gearbox gives you the speed difference.

Are there turbine engines with a gear box? I've never heard of one (except for geared turbofans, where the fan has a gearbox, or a turboprop, but never between compressor and turbine).

@Bianfable yes. Most large jet engine have three speeds. It improves the efficiency of the flow. Usually you have one slow shaft a medium speed shaft and a high speed shaft, but they all connect compressor and turbines, thus no gearbox. But the engines on the A220 for example have a gearbox for the fan. It is just a design choice of efficiency in flow vs transmission efficiency vs space and heat requirements.

"Most large jet engine have three speeds": Only RR Trent engines as far as I know. All others typically have two, not three. "A220 for example have a gearbox for the fan": Yes, I know, it's called a geared turbofan, as I said in my comment. But I have never seen a turbine engine with a gear box between the compressor and turbine, which would give those different speeds.


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How long does it take to refuel a Cessna Citation X+?
Does anyone have any sources that can tell the the number of fueling nozzles and the fueling rate for a Cessna Citation X+ or a Cessna Citation X?

Basically fuelling time depends on how fast the hydrant or fuel truck can deliver fuel.
This comes from SmartCockpit:

The  Citation  X  fuel  system  is  comprised  of  the  storage,
distribution,  refueling/defueling,and  indicating  systems.    The
storage  system  is  made  up  of  a  set  of  integral  tanks  in
each wing,  and  a  center  wing  tank  which  includes  a  forward
fairing  fuel  tank.    Each  wing  tank  has  a hopper  tank  which
is  integral  to  it.    The  two  wing  tanks  incorporate  check
valves  and  baffles allowing  each  wing  tank  complex  to  function
as  a  single  tank.    Other  integral  components  of the  storage
system  are  the  gravity  fuel  fillers,  drain  valves,  flapper
check  valves,  vent  system                      components,
positive/negative   pressure   relief   valves   and   all   of   the
associated   system plumbing.    Transfer  capability  is
incorporated  enabling  all  usable  fuel  to  be  available  to
either engine.Each  wing  tank  holds  a  total  of  521  gallons
(3518  Lbs.)  of  fuel,  which  includes  the  hopper tank.    The
center  wing  tank  holds  888  gallons  (5594  Lbs.),  207  (1397
Lbs.)  of  which  are contained  in  the  forward  fairing  tank.
Total  fuel  capacity  of  the  airplane  fuel  system  is
1927 gallons; at 6.75 pounds per gallon the available fuel weight is
13,031 pounds.
SINGLE-POINT REFUELING DEFUELING SYSTEM
The  single-point  refueling  system  is  provided  to  enable  the
airplane  to  be  refueled  or    de-fueled  more  safely  and
conveniently  by  connecting  to  one  port,  which  is  not  open  to
the atmosphere.      Advantages   of   a   single-point   refueling
and   defueling   include   minimized refuel/defuel   time,   reduced
possibilities   of   fuel   contamination,   reduced   static
electricity hazard, less airplane skin damage, and there is no
personnel contact with the fuel.The  refueling/defueling  system  is
independent  of  the  airplane  system.    It  is  designed  for
refueling  with  a  truck  or  refueling  hydrant  (pit)  having
single  point  provisions.    The  major components  of  the  system
include  the  refueling/defueling  adapter  (receptacle),  the
precheck control  panel,  refuel  shutoff  valves,  the  pilot
(precheck)  valves,  defuel  valves,  a  sequencing valve,   manual
defuel   select   shutoff   valves,   internal   drain   valves   and
associated   system plumbing.Single-point  refueling  is  accomplished
by  connecting  the  refueling  truck  or  refueling  pit equipment
to  the  airplane  at  the  single-point  refuel/defuel  adapter  on
the  right  side  of  the fuselage just forward of the wing leading
edge.

Just as a really general idea, however, single point fueling trucks fairly routinely have flow rates in the vicinity of 200-250 US gallons per minute.

So from empty to full would take about 10 minutes at the lower rate of 200 gpm